To put it simply, I will just pick one that both myself and the market like.

The topic both interest u, so u can work hard on it, and interet the market, so u will get profit from it.

The topic should be.....

Just Close ur eyes...concentrate.....
The first thing that come from your heart.....u should blog on....

There is a lot to think about when choosing a blog topic. After all you are going to be writing about it daily for a number of years so you have to choose something that you know you can last the distance with. Please feel free to check out my article 7 Tips for Choosing a Great Blog Topic

The Wizz
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